Safe wafer pick-and-place is a very important technical indicator for integrated circuit production lines. Generally, the breakage rate of wafers in the course of production due to wafer handling equipment should be less than 0.001%. Compared with a single-wafer processing system, a batch-type wafer heat treatment system requires more wafer transfer and pick-and-place operations in each production process, which makes higher demands of safe and reliable wafer transfer and pick-and-place.
Nowadays, robots have been widely applied in the field of semiconductor IC manufacturing technology and have become important tools in wafer handling systems for picking, placing and transferring unprocessed and processed wafers. The robot can response to instructions to accurate move to a point of wafer location in a three-dimensional or two-dimensional space to pick and place wafers.
Currently, the positional parameters of the robot during wafer handling in the batch-type wafer heat treatment equipment are generally obtained by offline teaching. The robot uses its fork to perform the pick-and-place operations to the wafers located in a wafer carrier according to the stored robot teaching data. However, factors such as equipment error, load variations or temperature variations may cause collision of the robot fork with the wafer or wafer carrier when the robot performs the pick-and-place operations, resulting in irreparable losses such as damages to the wafer or equipment.
Accordingly, in order to perform safe wafer pick-and-place operations, there is a need to calibrate or correct the offline teaching positions of the robot periodically.